B 1. FIELD OF THE INVENTION
The present invention relates to an easy-opening container and more specifically, to an improved retained tab affixed to the end wall of the container for opening it.
2. THE PRIOR ART
Easy-opening containers typically include a tap permanently joined to a tear strip, the latter being separable from the can top to provide an opening. Typically, the top is ruptured along a continuous score line and the tab and tear strip are removed as a unit and normally discarded.
The wide spread use of easy-opening containers has resulted in the littering of beach and picnic areas by an accumulation of discarded pull-tabs and tear strips. These discarded items are difficult to clean up because of their small size and because they are normally made of aluminum and therefore cannot be collected by magnetic means.
The can industry has responded to this ecological problem by developing a number of ingenious easy-opening containers in which the tab and tear strip are permanently retained to the can even after it has been opened. Typical cans of this type are are disclosed in: U.S. Pat. No. 4,030,631, issued June 1, 1977, to Brown; U.S. Pat. No. 4,024,981, issued May 24, 1977, to Brown; and U.S. Pat. No. 4,015,744 issued Apr. 5, 1977, to Brown.
Some states have ecology laws which forbid the use of a closure that separates from the can in the opening movement. The recently developed ecology cans disclosed in the above patents comply fully with such state laws. However, it has been found that the tabs can be broken off from the cans by successive flexing movements, and a few sightings of such broken-off tabs have been reported. In view of this continuing littering, some state regulatory agencies are imposing more stringent requirements upon the cans. To meet these requirements, it will be necessary for the tab to be retained to the can even after being subjected to a number of flexing cycles. Thus, an urgent need exists for an easy-open can having a tab which can withstand a number of flexing cycles without breaking off.
One approach to increasing the flexure endurance of the tabs is disclosed in columns 12 and 13 of U.S. Pat. No. 3,967,752, issued July 6, 1976, to Cudzik. Cudzik discloses a composite tab which includes an insert of a dead soft aluminum alloy. This insert, which has superior flexural endurance continues to retain the tab to the can even after the body of the tab, which is made of a stiff aluminum alloy, has failed due to flexural fatigue.
Because of its composite structure, the tab disclosed by Cudzik requires tooling for producing it which is substantially more expensive than the tooling required to produce the improved tab of the present invention.
The limited flexural endurance of the tabs disclosed in the patents issued to Brown referred to above is inherent in their structure. In those tabs, the repeated flexing is localized along a line adjacent the rivet by which the tab is affixed to the can end. Successive flexing cycles cause the material in this area of localized flexing to work harden, becoming brittle and breaking there. Except for its limited flexural endurance, the tab disclosed in the Brown patents referenced above is very attractive because of its unitary structure and relatively low cost of production.
Thus, it appears that an urgent need exists in the can industry for a retained tab having a unitary structure and capable of withstanding a number of flexing cycles.